[Aim]  To investigate the expression profile of the β-N-acetylhexosaminidase 4 gene (AmFdl) in different tissues and developmental stages of Apis mellifera workers, and to characterize the molecular properties and conserved domains of its encoded protein, thereby providing a foundation for the further functional investigation of this gene. [Methods]  The transcription of AmFdl was detected using RT-PCR followed by agarose gel electrophoresis, and its expression in various tissues and developmental stages was analyzed using RT-qPCR. The physicochemical properties, molecular features, conserved motifs and functional domains of AmFdl were predicted and analyzed using appropriate software, after which a phylogenetic tree was constructed. [Results]  AmFdl was differentially expressed in different tissues. Highest expression was in the hypopharyngeal glands, which was significantly higher (P < 0.05) than that in the brain, midgut, fat body, cuticle and venom glands. With respect to eggs and larvae, expression was highest in worker bee eggs, and thereafter gradually decreased with larval age. With respect to worker bees, expression was highest in 2-day-old workers, significantly higher (P < 0.05) than that in 1-day-old or 6-day-old workers, and lowest in 6-day-old workers. AmFdl encodes 717 amino acids, has a molecular weight of about 80.8 kD, an average hydropathy index of ﹣0.359, and does not contain a typical signal peptide. The FDL proteins of the Apis mellifera, Apis cerana, Frieseomelitta varia, Bombus vosnesenskii and Bombus impatiens, all contain the same two structural domains, GH20_HexA_HexB_like and Glycohydro_20b2, and AmFdl also have five conserved motifs. The FDL proteins of Apis mellifera and Apis cerana cluster together on the evolutionary tree. [Conclusion]  The AmFdl gene is predominantly expressed in the hypopharyngeal glands and eggs of Apis mellifera workers. AmFdl is a hydrophilic, non-transmembrane protein with conserved motifs and functional domains.